pedersen venous pressure measurement i. choice of zero level

8/3/2019 Pedersen Venous Pressure Measurement I. Choice of Zero Level

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Acta M.edica Scandinavica. Vol. CXLI, fasc. III, 1951.From the Medical Department B of the Rigshospitalet, Copenhagen, Denmark.(Chief: Professor Erik Warburg, M. D.)

Venous Pressure Measurement.I. Choice of Zero Level.

ByASGER PEDERSEN and JACOB HUSBY.

(Submitted for publication, May 15, 19M.)

Numerous publications on clinical measurement of the venous pressure haveseen the light of day during the past half century, but the procedures have differed widely and the results have often been conflicting. The inaccuracy of venouspressure measurement is due partly to the hydrostatic correction, partly to theapparatus, and partly to the failure to eliminate those factors in the physiologicalstate of the individual which may compromise the measurement. In the presentand a following paper the writers propose to deal with these three SDurces oferror and to describe a new method for direct venous pressure measurement bymeans of the T y b j ~ r g Hansen electric condenser manometer.

Reference Level (Zero Le\'el).In pressure measurements anywhere in the circulation two quantities may be

of interest: One is the locah pressure, i. e. the actual intravascular excess pressure as compared with the surrounding outer pressure at the given site and in agiven posture; the other one is the general clinical quantity, the venous pressureor the arterial pressure following correction for hydrostatic factors, i. e. measuredfrom a common reference level and under given external conditions. This correction is of little moment in the measurement of arterial pressure, but it is of theutmost importance in the measurement of the low venous pressures (and in pressure measurements during right cardiac catheterisations) and constitutes one of


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186 ASGER PEDERSEN AND JACOB HUSBY.curate placement of this initial level is bound to be arbitrary to a certain extent.I t is generally agreed, however, that for practical reasons the reference level oughtto be at the level where the diastolic filling pressure ends and the systolic excess pressure arises, i. e. on a level with the heart - in the case of venous pressureon a level with the right auricle - but there is little agreement as to the positionof the latter in the chest.Of course, the right auricle is of some extent. Its upper and lower borders - inthe horizontal position - are usually considered to be at the attachments of the3rd and 6th ribs to the sternum and its centre consequently at the sternal endof the 4th intercostal space. In the sagittal plane its extent (excluding the auricular appendage) is presumably somewhat larger than the posterior half of theheart shadow, seen from the lateral aspect. These data from topograhpic handbooks accord fairly well with experience from cardiac catheterisation and withthe findings reported by Lyons, Kennedy & Burwell (8). In cross sections of 14frozen cadavers they found the anterior border of the right auricle to be within40 to 50 mm of the anterior border of the thorax and the antero-posterior diameter of the auricle to be 40-70 mm; and Roesler (12), in an orthodiagraphicstudy of 150 normal subjects, found a sagittal extent of the heart shadow between63 and 107 mm.The level within the heart (or within the right auricle) from which the measurements are made is of subordinate importance, but the zero level naturally must,as far as possible, pass through the same level in the heart in all patients, regardless of the size of the chest.

The outer pressure to which the zero pressure is referred is usually the atmospheric pressure. It has been suggested, however, that for determination of theeffective venous pressure reference should be made to the negative intrathoracicpressure (4), but experiences from heart catheterisation have shown that the normal pressure in the right auricle corresponds fairly well to the atmospheric pressure (1, 2), and in the present paper, therefore, no regard is paid to the intrathoracic pressure.

Previous Investigations.Numerous and widely different zero levels have been suggested and employedin the measurement of venous pressure. Lyons, Kennedy & Burwell (8) havetabulated the reference levels used by various authors, compared with their methods and normal values. From among the numerous zero levels which have beensuggested in the course of time, the more well-defined ones are divisible into threegroups:(1) A fixed distance from the anterior surface of the chest: Lewis (7) measuredfrom the suprasternal notch proper. - Moritz & Tabora (9), experimenting on

the cadaver, found the entrance of the caval veins to be 5 cm posterior to the4th costo-chondral junction. - Bloomfield etal. (1) found the centre of the heart


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VENOUS PRESSURE MEAS[lREMEl'IT. I. CHOICE OF ZERO LEVEL. 187(2) A fixed distance from the posterior surface of the chest: Studying 14 cadavers Lyons, Kennedy & Burwell (8) found the posterior border of the right auricleto be 80-105 mm anterior to the skin of the back, and on fluoroscopic study of

42 normal subjects the posterior border of the cardiac shadow was 65-100 mmanterior to the skin of the back. They selected a zero level 10 em anterior to theback, and with this : r ~ f e r e n c e level they found an even distribution of higher andlower venous pressures on various thoracic diameters in 90 normal adults.(3) A measure relative to the antero-posterior diameter of the chest: Recklinghausen (10) proposed a zero level (for indirect measurement of the arterial pressure) at the centre of the chest at the xiphoid process. - The phlebostatic axis)}of Winsor & Burch (14) is the line of intersection between this plane which X-rayhas shown to correspond to the entrance of the caval veins into the auricle, anda plane through the 4th intercostal space adjacent to the sternum; their phlebostatic level is the horizontal plane through this axis, regardless of the posture.- Hooker & Eyster (6) selected the junction of the anterior and middle thirdsof the antero-posterior diameter of the chest. - The axillary lines have beenused also: Harris (3) suggested the anterior axillary line, Taylor, Thomas &Schleiter (13) the midaxillary line which also has been used in about 400 cardiaccatheterizations at the Medical Department B of the University Hospital inCopenhagen (2).Catheterizing the hearts of 5 patients Richards et al. (11) found the positionof the catheter tip in the right auricle to accord best with the zero levels of Lyonset al. as well as of Eyster, but their series is small and the position of the cathetertip in the sagittal extent of the auricle is not mentioned. Lastly, Holt (5) has suggested complete elimination of the hydrostatic factor by stating the venous pressure as the mean value of the pressures in the supine and prone position, usingthe same reference level (the spine). The zero point is then determined in eachindividual case as midway between the tops of the two columns of saline in thetwo pressure measurements; in 10 normal subjects this point was very close tothe centre of the thoracic depth. This procedure is interesting from a theoreticalpoint of view, but hardly applicable as a routine method.

Writers' InvestigntionsAccording to what has been stated above, the zero level must fulfil the following requirements: A plane which as far as possible passes through the samelevel in the heart of all patients and which is easy to find by means of externallandmarks. As a reproducible paine de repaire we chose the middle of the line connecting the junction of the two caval veins with the right auricle. We tried todetermine the position of this point in the chest in the horizontai posture by

making X-ray films during cardiac catheterization, when the catheter had beenpassed through the superior caval vein and the right auricle and was reachingdown into the inferior caval vein.1


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188 ASGER PEDERSEN AND JACOB HUSBY.

Fig. 1. One of the X-ray films, lateral view, with catheter through right auricle into inferior cavalvein. The (a) anterior sui-face and (f) posterior surface of the body, (b) anterior border and (d) posterior border of the heart shadow, (c) catheter in the right auricle, and (e) anterior surface of the vertebral column are plotted on a line drawn horizontally from the small piece of lead gum in the fourthintercostal spaoe (cf. Table I) .The films are true lateral views, the patient lying on his back on a flat couch

and the tube centred, by means of a water level, horizontally on a level with themiddle of the chest, the cassette being placed vertically against the lateral aspectof the chest as high up in the axilla as possible. For technical reasons it was impossible to obtain a focal-film distance longer than 11/2 m, but the position ofthe catheter near the median axis of the chest (in the sagittal as well as the frontal plane) reduces the consequent distortion. The films were made in mean inspiration and exposed for 31/2-41/2 seconds, i. c. through all phases of the cardiaccycle. The films show the catheter stretching through the auricle as a direct connection between the entrances of the caval veins (i. e. taking an oblique downward and backward course, since the superior caval vein is always anterior to theinferior caval vein).On the films all the measurements were done on a level with the fourth inter


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189EYOUS PRESSURE MEASuREMENT. I . CHOICE OF ZERO LEVEL.connecting the entrances of the two caval veins. The results of the measurementsand the patients' data will be seen in Table 1.The present series of 18 patients differs from previous studies on the locationof the zero point in including several children and young adults. In four patients(Cases 3, 4, 10, and 11) X-ray showed enlargement of the right auricle which wasconfirmed by catheterization; all had an elevated auricular pressure (measuredfrom the midaxillary line). Case 16, moreover, exhibited a doubtful increase inauricular pressure without signs of auricular enlargement. In these patients, theposition of the catheter in the chest did not differ significantly from that in theother cases, where no abnormality of the right auricle was found. Cases 10 and11, however, represent some of the extreme values at both ends.

The distance of the catheter from the anterior surface of the chest ranged from63 to 111 mm, averaging 91 mm with a standard deviation of 13.7 mm. The distance to the back ranged from 88 to 170 mm, averaging 122, with a standarddeviation of 16.9 mm - i. e. the mean error in per cent would be about the same(14-15 % of the distance), if the zero level in these patients were to be placedat a fixed distance from the anterior or posterior surface. I t is clearly apparentfrom the figures, however, that the distance of the catheter from the anterior andposterior surface is a function of the antero-posterior diameter of the chest. Theratio distance of catheter from anterior surface

antero-posterior diameter of the chestvaries from 0.38 to 0.49, averaging 0.427 with a standard deviation of 0.029. Inother words, by using this average quotient, it is possible to calculate the positionof the catheter with a mean error of about 3 % of the thoracic diameter. Therewas no significant difference in the size of this quotient in large and small chests:the average for the 8 patients with a diameter smaller than 21 em was 0.434 andfor the 10 patients with a diameter exceeding 21 em 0.422 .

In the measurements to be reported below, therefore, we chose a zero level ata distance of 0.43 times the depth of the chest below the anterior surface of thesternum on a level with the fourth intercostal space. No difficulties are connectedwith employing this average value as a zero level, if the quotients correspondingto ordinary diameters between 15 and 30 em are written down beforehand (e. g.on the water level used in the adjustment). To obtain a simpler conversion, themiddle of the chest depth, measured at the same level, may also be used. Thiswill result in 1 to 2 cm higher pressure.

I t is most practical to measure the diameter of the chest with an obstetricalpelvimeter, while the patient is sitting normally (not straightening his back)and breathing normally. Repeated measurements showed no definite differencebetween the diameter of the chest in the sitting and horizontal position, when


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191ENOUS PRESSURE MEASUREMEl'iT. 1. CHOICE OF ZERO LEVEL.I.into Inferior Caval Vein. All Measurements at the Level of the Sternal End of the FourthSpace. .

I Measured Measured on the X-ray Film:i on the I Distance from Anterior Surface of Thorax to:Pressure in Patient:Right Auriclemm Hg Ant.-post. Ant.-post. Catheter Ant. SurfaceIAnt. Border I Post. BarderDiam. of Diam. of in Right of Vertebralof HeartThorax Thorax I of Heart I Auricle Columnnot measured 13.0 em 15.1 cm 1.7 cm 6.3 cm 7.6 em 8.6 cm I- 3 to + 4 14.0 16.2 1.5 .) 6.5 8.4 9.5 + 4 to + 12 15.0 16.8 1.5 ,) 6.5 lOA ,) 11.0 I

II+ 9 to + 18 16.0,) 19.4 2.5 9.6 12.0 12.3 i+ 5 to + 10 17.0 2004 1.7 9.1 11.2 ,) 13.2 -2 to + 4 17.0 20.6 2.0 9.1 10.5 13.5 -3 to + 3 17.0 20.7 2.4 8.6 10.3 11.8 +3 to + 6 18.0 20.8 2.3 ,) 9.8 10.7 .) 12.1 + 2 to + 6 18.0,) 21.4 2.5 9.4 ,) 11.0 12.3 + 7 to + 22 19.0,) 21.7 2.3 9.3 12.0 14.5 + 5 to + 17 18.5,) 22.0 1.8 ,) 10.2 11.9 13.2 I

o to + 7 18.0,) 22.5 2.3 ,) 9.5 12.0 13.5 + 4 to + 10 20.0,) 23.0 2.1 ,) 9.3 12.3 13.8 - 3 to + 4 19.5 23.3 2.8 9.3 11.5 ,) 13.5 + 2 to + 7 20.5,) 23.5 2.1 9.9 12.8 14.8

o to + 12 20.0 24.1 3.2 ,) lOA 12.8 15.1 +4 to + 9 23.5 25.8 2.3 11.1 13.7 16.5 .)+ 2 to + 8 25.0 27.5 2.1 10.5 15.0 18.3

Mayo Clinic 23: 316, 1948).the marked deviation between the various reference levels, particularly in casesof large chests (at a diameter of 30 em, for instance, the reference level of Moritz


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192 .ASGER PEDERSEN .AND J.ACOB HUSBY.~ J Z f ~ r o - J ' l o s i e 1 " l ' o r IJr'crmeier a/ lJzorcrx tDzeasured an X -ro:.Picture}1 a $I I I I

ri .lIearlSftadow 1 5

A Anterior$ur/IZi!ea Verle.hra:l Col=.. .

fO

A

" . H ~ ........" . Wu...." " 4 . l l ~ .f j '.lJi.danc:e /,elo>v kisr,"", Surface afThorar..

Fig. 2. Diagram of the measurements in Table I, compared with some of the commonly used referenceleve;.terior and middle third of the chest falls about the middle of the heart shadow,i. e. presumably somewhere in the anterior part of the auricle. Bloomfield and co-workers' statement that the middle of the heart shadow is 5 cm below the angleof Louis is not directly comparable with our results, since our measurements weremade from the level of the 4th intercostal space. The zero level of Lyons, Kennedy& Burwell 10 cm above the couch is in a fairly constant relation to the anteriorborder of the vertebral column (in the adults), but the distance from the catheterincreases considerably in the thick-chested subjects.The situation of the axillary lines was studied in 15 males and 15 females,selected at random among the patients in the department, excluding, however,subjects with deformities of the chest or of the vertebral column. The patientwith the largest thoracic depth (32 cm) was suffering from emphysema. The antero-posterior diameter of the chest was measured with an obstetrical pelvimeteron a level with the fourth intercostal space anteriorly, the distance of the anterior and midaxillary lines from the anterior surface of the chest (average ofright and left side) was determined at the same level. As will be seen from Fig. '3,these determinations carry a considerable deviation - at least in our hands


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193ENOUS PRESSURE MEASUREMENT. 1. CHOICE OF ZERO LEVEL.

}fen W6.m.en 0 AnierzOrAxd!aryLine ' " ,t,. i'1zd=ilta-ry Line

0 05 0 0 0 0 0 0 0 0 o o10

.4A AA

lies/ana' ~ e l o w Anferlor Surfaceo f 'lJwraxo.

Fig. 3. Diagram of the position of the anterior and midaxillary lines in 15 men and 15 women,-compared with the reference level used in the present study.

'rable II.Venous Pressure (mm of Water) Referred to Different Zero Levels in Forty Normal Adults.I Thoracic Diameter Thoracic Diameter18--20'/. em 21-26 emI (9 men and 12 women) (13 men and 6 women)

I Mean I Range Mean I RangeI I Measured from here suggested zero level (0.43 X_ thoracic diameter) . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 I 71-100 I 90 I 70-106

Referred to zero level of Moritz & Tabora . . . . . . I 56 39- 67 43 23- 641 1 1

Referred to zero level of Eyster . . . . . . . . . . . . . . . . , 68 1 54- 81 I 68 I 50 - 84Referred to zero level of Recklinghausen . . . . . . . . 100 84-114 106 85-123

1 1 1

Referred to zero level of L ons Kenned & Burwell 76-114 117 90-144___________y______ __9 _ 7 _ ~ ___ _ _ _ ~ I ~ . _______the anterior fold of the


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194 ASGER PEDERSEN AND JACOB HUSBY.other regardless of the anatomical differences, especially the size of the chest.With the technique described in the following paper we have measured the venouspressure in forty adults, partly normal test subjects and partly patients in thedepartment with slight and irrelevant disorders (myopathies, gastro-intestinaldisturbances) and with normal electrocardiogram and X-ray configuration of theheart. I t will appear from table II that the best accordance between the valuesin patients with small and large chests and the smallest range was obtained withthe reference levels fixed as a measure relative to the size of the chest.

Summary.The problem of establishing a common reference level for pressure measure

ments in the circulation has been investigated.X-ray films made during cardiac catheterisation in 18 patients (includingchildren) have shown the centre of the line joining the entrances of the two caval

veins into the right auricle to be an average distance of 0.43 times the thoracicdiameter from the anterior surface of the chest, the mean deviation being only3 % of the thoracic diameter. This average value (or half the thoracic diametermeasured on a level with the fourth intercostal space anteriorly) is proposed asthe reference level of venous pressure measurement in the supine position.

This reference level has been compared with some of the commonly used reference levels and with the position of the axillary lines.In 40 normal subjects the venous pressure measured from this reference levelshowed no significant relationship to the thoracic diameter.

References.1. Bloomfield, R. A., H. D. Lausen, A. Cournand, E. S. Breed & D. W. Richards:J. Clin. Investigation 25: 369, 1946. - 2. G0tzsche, H. & E. Warburg: Acta med. scan

dinav. 1951 (in press). - 3. Harris, 1.: Edinburgh M. J. 35: 630, 1928. - 4. Henderson,Y. & T. B. Barringer: Am. J. Physiol., 31: 352, 1913. - 5. Holt, J. P.: Am. J. Physiol.,130: 635, 1940. - 6. Hooker, D. R. & J. A. E. Eyster: Bull. Johns Hopkins Hosp., 19:274, 1908. - 7. Lewis, T.: Brit. M. J., 1: 849, 1930. - 8. Lyons, R. H., J. A. Kennedy& C. S. Burwell: Am . Heart J. 16: 675, 1938. - 9. Moritz, F. & D. von Tabora: Deutsches Arch. f. klin. Med. 98: 475, 1910. - 10. von Recklinghausen, H.: Arch. f. exper.Path. u. Pharmakol. 55: 375, 1906. - 11. Richards, D. W. jr., A. Cournand, R. C. Darling & W. H. Gillespie: Tr. A. Am. Physicians 56: 218, 1941. - 12. Roesler, H.: Am.J. RoentgenoI. 32: 464, 1934. - 13. Taylor, F. A., A. B. Thomas & H. G. Schleiter:Proc. Soc. Exper. BioI. & Med. 27: 867, 1930. - 14. Winsor, T. & G. E. Burch: Proc.Soc. Exper. BioI. & Med. 58: 165, 1945.

pedersen venous pressure measurement i. choice of zero level

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